Many known apparatuses such as optical transmission apparatuses and communication apparatuses include shelf units. A shelf unit can receive a number (about 20) of plug-in units (PIUs) and interface boards (hereinafter referred to as “printed boards”) having different functions. A printed-board-receiving structure employed in a known shelf unit will now be briefly described with reference to FIGS. 13 to 14B.
FIG. 13 is a perspective view illustrating the appearance of a known shelf unit. FIG. 14A is a perspective view of a printed board to be used with the known shelf unit. FIG. 14B is a longitudinal sectional view of relevant parts of the printed board illustrated in FIG. 14A.
Referring to FIG. 13, a casing body 2 of a known shelf unit 1 can receive therein a plurality of printed boards 3. The casing body 2 of the shelf unit 1 is made up of a top board 5, a bottom board 6, a left-side board 7, a right-side board 8, and a back wiring board (hereinafter referred to as a “backboard”) 9 provided at the back of the casing body 2.
The backboard 9 of the shelf unit 1 is provided with connectors 10 fixed at particular positions thereof. The connectors 10 each engage with a connector 4 provided on a printed board 3 to be loaded into the shelf unit 1, thereby becoming electrically connected thereto.
Referring to FIG. 13, the bottom board 6 of the shelf unit 1 is provided with guide rails 11 each having a rectangular groove 12. The printed boards 3 are loadable into the casing body 2 in order along the grooves 12. The widths of the rectangular grooves 12 of the guide rails 11 are set to be the same as the thicknesses of the printed boards 3 to be loaded.
The thicknesses of printed boards vary because the numbers of layers of the printed boards also vary with the numbers of components to be mounted on the printed boards. Accordingly, the rectangular grooves 12 of the guide rails 11 provided in the shelf unit 1 are to be processed such that the widths thereof match the thicknesses of different kinds of the printed boards to be loaded.
The known printed-board-receiving structure employs adapters, which are to be attached to the printed board. Referring to FIG. 14A, adapters 14 each have a rectangular groove 16 and a projection 15 whose widths are substantially the same as the thickness at an end of a printed board 13.
Specifically, the adapters 14 can be attached to the printed board 13 by fitting the ends of the printed board 13 into the rectangular grooves 16 of the adapters 14. Each of the adapters 14 is secured to the printed board 13 with a screw 17, and the projection 15 of the adapter 14 is fitted into the rectangular groove 12 (FIG. 14B) of the guide rail 11. Thus, different kinds of printed boards are loadable into the shelf unit 1.
In the known art, in the case where printed boards having different thicknesses are to be loaded into a shelf unit, grooves of guide rails provided in the shelf unit are processed so as to have widths matching the thicknesses of the printed boards, or adapters that can be received by the guide rails having a common width are attached to the printed boards.
Another exemplary printed-board-receiving structure is disclosed in Japanese Unexamined Utility Model Registration Application Publication No. 07-14690. The structure includes substantially V-shaped guide rails extending in a direction in which printed boards are loaded, and stoppers and handles with which the printed boards are positioned.
Yet another exemplary printed-board-receiving structure is disclosed in Japanese Unexamined Patent Application Publication No. 11-68350. The structure includes a frame having a groove so as to hold a circuit board, whereby malfunction of the circuit board is prevented.